1. Field of the Invention
The invention relates to a configuration for supporting a first part of the stator of an electric machine, in particular of the stator of a turbogenerator, at a second part of the stator.
In electric machines, such as generators, for converting mechanical energy into electrical energy or vice versa, a rotor shaft rotates during the energy conversion, in a stator cavity that is generally approximately rotationally symmetrical. A number of different turbogenerators are described in a document issued by Kraftwerk Union AG, Mulheim/Ruhr, Germany, Order No. K/10437-01 dated March 1982 (referred to below as the KWU document). Another document, in which turbogenerators and parts of turbogenerators are described, was issued by Siemens AG, Bereich Energieerzeugung [Power Generation Division] (KWU) Freyeslebenstr. 1, D-91058 Erlangen, Germany under the Order No. A96001-U111-A244 (referred to below as the Siemens document) in September 1993. Both documents describe stator electrical windings which have so-called winding overhangs at one or both axial ends. Stator winding overhangs of hydrogen-cooled turbogenerators may be supported with the aid of a solid supporting ring, which is preferably formed of glass fiber-reinforced plastic and is approximately rotationally symmetrical. The supporting ring is in turn supported on a pressure plate, through the use of which a laminated core of the stator is held by core pressure. The laminated core is used to reinforce the magnetic field in the stator winding. In that case the stack direction is approximately parallel to the axis of rotation of the rotor shaft. The support between the supporting ring and the pressure plate has a number of functions. On one hand, in the vertical direction, it bears the natural weight of the supporting ring and that of the parts which are supported by the supporting ring, in particular the winding overhang. On the other hand, it prevents the winding overhang from twisting during operation of the turbogenerator or in the event of a defect. In addition, it has other functions, such as damping of oscillations which occur during operation of the turbo-generator and compensating for distance changes and relative displacements of parts of the stator caused by thermally dependent expansion and contraction.
Supports are known which are constructed especially for the purpose of carrying out certain of the functions already mentioned, for example friction bearings specifically for absorbing the force resulting from the weight of the supporting ring and of the winding overhang. The overall support includes a multiplicity of components of different types. The multiplicity of components require an area which is at the expense of the area available for other parts disposed in the region of the pressure plate and of the supporting ring. In addition, the interaction of the individual components necessitates appropriate precision in their production.
German Published, Prosecuted Patent Application 1 057 214 specifies a device on single-phase, high-power alternators for sprung torque transmission from the stator to a machine foundation, with the inclusion of spring elements disposed between an iron body of the machine and an outer housing. The spring elements, which act on both sides of the periphery of the iron body fitted with the winding, are in the form of spring supports or spring columns and are supported on parts of the outer machine housing which are themselves supported like brackets on the foundation. That is done in such a way that vibration forces which occur are absorbed on housing parts supported rigidly on the foundation, and are transmitted to the foundation.
German Published, Prosecuted Patent Application 1 164 560 discloses a housing casing for electric machines having longitudinal ribs which are disposed between the housing casing and the laminated stator core, are distributed approximately uniformly around the circumference of the laminated core and are located with their cross-section in a direction other than the radial direction with respect to the longitudinal axis of the housing. In that case, the direction of at least some of the ribs (which are provided with at least two stiffening rings) deviates alternately to one side or the other of the radial. A total sum of the mean deviations from the radial to one side is approximately equal to a total sum of the angular deviations from the radial to the other side.
German Published, Prosecuted Patent Application 1 220 022 discloses an electric machine having a cylindrical stator housing, in which rings are disposed at ends of the stator housing in order to damp oscillations. In that case, the stiffness of the rings is greater than that of the stator housing and they are connected by connecting a device (which is disposed at a plurality of locations distributed around the circumference) to the stator housing. That is done in such a manner that, in the event of any relative movement between the rings and the end surfaces of the stator housing, friction forces are produced which counteract the housing oscillation.
German Published, Non-Prosecuted Patent Application DE 37 07 422 A1 relates to a method for the attachment of the stator core in an electrical three-phase alternator, in which a clamping ring is disposed on the outer circumference of the stator core, and that clamping ring is firmly connected to the stator core, at least at predetermined locations. Furthermore, alternator housing parts are brought into contact with the clamping ring, and are braced with respect to one another, on both sides of the clamping ring. The clamping ring has axial passages, preferably formed by a sheet-metal strip which forms the clamping ring having a general corrugated shape. In that way, the internal channel cross-section for the cooling air which flows through the alternator is varied by the various options for the contact between the annular surfaces of the housing on both sides.
Swiss Patent 547 568 discloses a holding device for the stator of a dynamo-electric machine. The stator is disposed between a pair of end frames within a non-load-bearing outer casing. The holding device is used to isolate stator vibration from other parts of the dynamo-electric machine. The holding device has at least one pair of vertical spring plates which are disposed on opposite sides of the stator. One end of each spring plate is attached to the stator and the other end of each spring plate is attached to a load-bearing foundation. The non-load-bearing outer frame, which is disposed around the stator between the end frames and has no contact with the spring plates and the stator, is constructed in such a way that stator vibration can be transmitted directly to the foundation, and not to the outer frame.
Soviet Union Inventor's Certificate 843101 shows a stator of a hydrogenerator. The stator is hung in a frame. The frame is formed by annular components which surround the stator and to which the stator is fastened through bendable clamps.